The present invention relates to controlled inlet valves for metering pumps.
To inject metered amounts of liquid into another liquid, it is known to use a metering pump which consists of a cylinder in which moves a piston. The piston draws the liquid to be metered from a container and pumps it into a second container which holds the other liquid. The second container may in particular be an injector device as described in French Patent Application No. 72.39699.
However, if a valve of a conventional type which opens under atmospheric pressure is used at the inlet when the fluid pressures involved are very low, this results in the valve closing in an unsatisfactory fashion and the metering action being such that the metering device operates incorrectly.
It is an object of the invention to provide a device which shall minimise or overcome these disadvantages by the use of a positively controlled valve.